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    <title>HTML调试</title>
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    <p>HTML如何出错？</p>
    <ul>
        <li>未闭合元素：元素<strong>没有结束标签，会影响下边区域。</strong></li>
        <li><strong>错误嵌套：<strong>非常重要 <em>重点强调 </em></strong><em>这是什么？</em></strong></li>
        <li><strong>未闭合属性：如</strong></li>
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